Confinement effects in topological photonics

Photonic topological insulators have polarized edge states which support unidirectional propagation of light. In practice, one would like to make devices exploiting these states as small as possible. In this work we theoretically investigate the effects of confinement on topological edge states using a particular photonic crystal design as an example [1]. We show that the edge bands become discretized but still support the unidirectional propagation which can be switched with the polarization. An analytical formula is derived which predicts the number of edge states and their field profiles agreeing with numerical simulations. These results will be relevant for experiments on topological photonic crystals containing less than a few hundred unit cells.

[1] G Siroki, P A Huidobro, V Giannini, Phys Rev B 96, 041408(R) (2017)